So I've got yet another problem on my 1999 5.4 f-150 that I need help identifying. My car gets up to temperature just fine and never overheats. However yesterday I tried to turn on the heater after the engine was completely warmed up and it just blew cool air. Today I was able to get it to blow hot air after messing with the switches a bunch, but now my A/C only blows hot air. I am able to get them to switch back eventually, but only after constant fiddeling.

The heater core hoses are both hot to the touch as well as the upper radiator hose after a drive on the freeway. Do these sound like symptoms of a failing blend door? I really hope not.

 

that is the same trouble i have, and when it gets closer to fall, im gonna tear apart the dash and fix it...im gonna replace the heater core, blend door, and blend door motor while im in there.....i really dread having to do it, but it must be done....good luck

 

I've been doing research on the "heater treater" and I think I am going that route.

 

I installed the Heater Treater in my '98 just yesterday, and I"m very pleased with the result. I was a little leary of cutting the plenum box since it's kind of flimsy anyway, but it seals up just fine. The factory door uses foam to seal off the heater core, and the HT uses neoprene, but it does the job well. I tested function with the plenum box still open and it works very nicely. I even took the time to take apart the blend door motor to check the gears, and everything looked fine. With a fix like this available, I wouldn't even consider pulling out the dash.

 

I recently did the fix as well, and I am happy with it too. Not only is it easier than pulling the dash, but it is a metal part instead of plastic. Making it less likely that you'd have to do it again.

 

I installed the Heater Treater door just the other day. It is quite a slick repair. The door with the two part hinge system is slick. Works great. I have to admit though, cutting the dash apart was tough and not something I wanted to do, but the alternative was much worse. I didn't want to pay the dealer the reported $1000 dollars or more to repair and I wasn't about to tackle tearing the dash apart myself. With my luck, after getting it together, there would have been problems with one of the gauges, or dash rattles, who knows what all could get messed up. It took about two hours to repair. A large portion of that was spent debating on whether or not I really wanted to cut through the dash. Once I got over that the whole job was a snap. The heat and AC now works great. Unless you believe your have a show truck, I say forget ripping out the dash.

 

i've replaced multiple blend door motors past few weeks at the dealership and on the 150's its a breeze 20-40 minutes tops, now on the 250's those required a bit more tearing down and removing air ducts to be able to reach the blend door motor's. iirc ford pays us tech's 0.8 hr to do it. so $1000 is far-fetched.